Against the backdrop of the spread of the Internet, improvement in the speed of the packet transfer device, such as a router and a switch that constitute a network is being sought. Each of the router and the switch is equipped with plural input lines and output lines, determines the output line from a destination address in a header upon input of a packet from the input line (hereinafter, this processing is called an output destination determination processing), and transfers the packet to the output line.
In order to increase the speed of the packet transfer device, it becomes necessary, for example, to increase the number of semiconductor devices, such as ASIC (Application Specific Integrated Circuit), or to raise its frequency, and therefore there is often the case where its power consumption increases with the increase of the speed of the router and the switch. For this reason, it is sought to reduce the power consumption and minimize an increase of electric power accompanying with the increase of the speed.
One of implementation systems for reducing the power consumption of the packet transfer device is, for example, described in JP-A-Hei11 (1999)-088458. This document describes that the packet transfer device thereof monitors existence/absence of a link connection of plural lines with which it is equipped and turns on a power supply of a port control circuit for performing packet processing when the link connection exists. By turning off the power supply of the port control circuit that does not needs to perform the processing, reduction in the power consumption of the packet transfer device is realized.
An other implementation system of reducing the power consumption of the packet transfer device is described in, for example, JP-A-Hei11 (1999)-234344. The packet transfer device of this document has plural interface ports that accommodate lines, an access state monitoring unit for monitoring access states of the interface ports, and a power supply control unit that decides whether the each interface is energized according to a monitoring situation of the access state monitoring unit. By turning off the power supply of the interface port that has no access, the reduction in the power consumption is realized.